t\  I  7-  TO  + 


Issued  March  7,  MO. 


U.S.  DEPARTMENT  OF   AGRICULTURE, 

ftUREAU  OF  PLAJST  INDUSTRY    (uvula,   Xo.  52. 
H.  r.  1. allow  ay,  1  hi.  r  of  Bureau. 


WART  DISEASE  OF  THE  POTATO 

\  pANGEROUS  EUROPEAN  DISEASE  LIABLE  TO  UK 
INTRODUCED  INTO  THE  UNITED  STATES. 


W.  A.  ORTON,  Pathologist, 


ETHEL  ('.  FIELD,  9<  u.vmic    Assistant, 

Cotto*    wi>  Truck  Diseases  and  Sugar-Plant 

Investigations. 


•jiiit.;— 10 


WMMINO- 


M         ~~| 


i 


BUREAU  OF  PLANT  INDUSTRY. 


Chief  oj  Bureau,  Beverly  T.Galloway. 
Assistant  Chief  of  Bureau,  G.  Hakold  Powell. 
Editor,  .1.  E.  Rockwell. 
'  lii: /  Clerk,  James  E.  Jones. 
[Cir.  52] 

2 


H    I     [.— 560. 


WART  DISEASE  OF  THE  POTATO; 

A  DANGEROUS  EUROPEAN   DISEASE  LIABLE  TO  BE  INTRO- 
DUCED INTO  Till-:  UNITED  STATES. 


INTRODUCTION. 

A  new  disease  of  the  potato  which  has  been  exciting  alarm  in  Europe 
i-  likely  to  in'  introduced  into  this  counl  ry  at  any  time  'This  circular 
is  issued  t<>  call  the  attention  of  American  growers  and  importers  of 
potatoes  to  this  danger  and  to  urge  their  cooperation  in  an  effort  to 
prevent  it  from  securing  a  foothold  here.  It  is  important  that  any 
cases  discovered  he  promptly  reported  and  all  possible  means  taken  to 
prevent  its  occurrence. 

DESCRIPTION  OF   THE  DISEASE. 

The  disease,  which  has  been  known  as  '"warty  disease,"  "black 
scab,"  "canker."  and  "cauliflower,"  is  one  which  attacks  the  tuber 
principally,  and  consequently  is  not  observed  until  harvesting  time. 
In  a  bad  attack  of  the  disease  big,  dark,  warty  excrescences,  sometimes 
as  large  as  the  tuber  itself ,  appear  on  its  sides  or  ends.  "Thegrowth 
consists  here  of  a  ma--  of  coral-like  or  more  or  less  scabby  excres- 
cences or  nodules,  similar  in  appearance  to  the  well-known  crown  or 
io.it  gall  of  apple-.  The  adherent  earth  can  he  easily  washed  oil' 
when  the  character  of  thegrowth  becomes  more  apparent.  It  is  not 
spongy  and  not  detachable  from  i  he  tuber.  It  i-  of  a  somewhat  lighter 
color  at  the  base  and  dotted  with  minute  rusty-brown  spots  over  the 
surface.  In  an  advanced  stage  the  tubers  arc  wholly  cov- 

ered by  this  growth,  ha\  ing  lost  every  resemblance  to  potatoes.  The\ 
are  lumps  of  irregular  outline,  never  spherical  or  oblong,  hut  simply 
a  mass  of    ragged  and  edged   excrescences.  A  -till  more 

advanced  stage  occurs  when  the  fungus  ha-  utilized  every  particle  of 
food  stored  in  the  tuber  and  has  reduced  it  to  a  brownish-black  soft 
mass  giving  off  a  very  unpleasant  putrefactive  odor.  Tin-  is  the  most 
dangerous  stage  of  the  disease,  and  the  tubers  which  have  reached  it 
can  not  be  harvested  whole.  They  break  in  piece-,  ami  thus  the  hrow  n 
ish,  pulpy  ma--,  consisting  almost  entirely  of  spores  of  the  fungus 

lClr.52] 


4  WART    DISEASE   <>F   THE   POTATO. 

and  remains  of  the  cell  walls  of  the  potato,  is  broken  up,  the  spores 
are  liberated  in  millions,  and  the  land  is  badly  infected  for  years." 
(Giissow,  L909.)     (See  Pis.  I  and  II.) 

In  a  mild  attack  the  eyes  first  appear  grayish,  then  turn  brown,  and 
finally  black,  while  in  a  healthy  tuber  these  are  whitish  or  purplish  in 
color.  The  tuber  is  only  slightly  disfigured  and  its  keeping  qualities 
do  not  seem  to  be  impaired. 

While  the  tuber  is  the  part  of  the  plant  chiefly  affected,  infection 
may  take  place  in  all  the  }Toung  tissues  of  the  plant,  the  roots,  stolons, 
stems,  and  even  the  leaves. 

THREATENING  NATURE  OF  THE  DISEASE. 

All  reports  indicate  that  the  potato  wart  is  one  of  the  most  serious 
of  all  known  diseases  of  the  potato.  It  converts  the  tuber  into  an 
ugly,  irregular,  and  utterly  unsalable  growth.  When  established  in 
a  field  it  may  affect  the  entire  crop,  and  the  land  remains  so  Infected 
that  potatoes  can  not  be  successfully  grown  for  six  or  more  years. 

We  quote  from  writers  abroad  the  following: 

J.  W.  Eastham  (Yearbook,  College  of  Agriculture  and  Horticulture, 
Holmes  Chapel,  lDO-i-):  "When  once  established  in  the  land  it  is  use- 
less to  grow  potatoes  again  until  the  pest  has  been  starved  out  or 
otherwise  destroyed;  but  so  far  as  is  known  no  other  crops  are  liable 
to  be  attacked.  Quite  the  worst  case  seen  in  Cheshire  occurred  on 
land  that  had  not  borne  potatoes  for  six  years;  'seed'  from  the  same 
source  as  that  employed  on  this  land  yielded  satisfactory  results  else- 
where, indicating  that  spores  were  not  introduced  by  the  seed,  whilst 
the  manure  employed  started  no  infection  elsewhere.  This  indicates 
prolonged  vitality  on  the  part  of  the  fungus,  which  would  render 
starving  out  a  very  tedious  process." 

E.  S.  Salmon  (Gardeners'  Chronicle,  litdT):  '"It  is  quite  clear, 
however,  that  the  'black  scab'  disease  threatens  to  inflict  such  serious 
injury  on  the  potato  crop  as  to  warrant  the  Board  of  Agriculture 
taking  official  action.  *  *  *  The  disease  is  viewed  with  alarm  by 
both  the  scientific  and  the  practical  man,  and  yet  no  steps  arc  being 
taken  to  deal  with  this  pest  which,  if  it  is  allowed  to  spread  through 
the  country  and  to  reach  Ireland,  will  cause  losses  of  hundreds  of 
thousands  of  pounds." 

Borthwick  (1!K)7),  retelling  to  an  outbreak  in  Scotland,  says:  "The 
whole  crop  was  damaged  to  the  extent  that  they  could  not  be  used. 
They  were  quite  useless,  the  early  varieties  being,  if  anything,  worse 
than  the  late,  especially  the  early  kidneys.  The  disease  was  first 
noticed  when  the  new  potatoes  began  to  form.  It  first  appeared  on 
the  stems  as  a  greenish  looking  canker,  which  attacked  the  tubers  as 
they  grew  and  soon  made  them  a  mass  of  corruption." 

[Cir.  52] 


C»    52,  Bureau  oil' 


Plate  I. 


Potato  Plant  Attacked  by  Wart  Disease.    iAfter  GussowJ 


Digitized  by  the  Internet  Archive 
in  2013 


http://archive.org/details/wartpotOOunit 


w  \i;t   DISEASE   OF   THE    POTA  m.  ,r) 

M.  C.  Potter  (Gardening,  L908):  "  From  ;ill  accounts  the  disease  is 
spreading  rapidly  in  the  infested  area-  and  the  amount  of  damage  is 
yearly  increasing.     *  In  certain  allotments     *    *     *     it   lias 

been  found  impossible  to  grow  potatoes." 

John  Percival  (1909):  "Potato  warl  has  already  become  a  serious 
trouble  in  many  districts  in  this  country,  ami  it  is  likely  to  develop 
into  the  worsl  pest  with  which  the  grower  will  have  to  deal  unless 
vigorous  measures  are  adopted  to  stamp  it  out." 

T.  Johnson  (1909):  '"  It  need-  only  a  very  casual  acquaintance  with 
the  fact-  of  the  case  in  the  British  I-les  from  the  time  of  the  discotery 
of  the  trouble  by  Potter  in  1!"^  to  the  present  time  to  warn  one  of 
the  necessity  of  taking  all  possible  steps  to  stamp  out  a  disease  which 
may  become  as  serious  as  ordinary  leaf-blight  and  less  amenable  to 
treatment.  it  i-  now    found  in  many  districts  in  England, 

Wale-,  and  Scotland.  It  is  often  mi  pronounced  as  to  destroy  the 
whole  crop,  and  it  is  not  confined  to  garden  plots.  Warty  tubers  are 
naturally  poorer  in  food  matter  than  healthy  ones,  and  when  not 
destroyed  in  the  held  do  not  keep  well  in  store.  They  oughl  to  be 
destroyed  as  Boon  as  found,  and  on  no  account  saved  for  seed." 

The  Gardeners' Chronicle,  1908:  "This  disease  *  *  *  is  excit- 
ing -ome  alarm  in  Germany,  where  it  is  said  to  be  spreading.  It 
appeal-  to  have  been  recognized  as  of  local  occurrence  for  some  time 
in  the  neighborhood  of  Diisseldorf,  Elberfeld.  During  this 

season  it  ha-  proved  so  injurious  a-  to  have  ent  irely  dest  roved  the  crop 
in  many  gardens  where  potatoes  have  been  raised  year  by  year." 

I  )r.  ().  Appel  (1908),  on  the  other  hand,  says:  "According  to  reports 
of  Spieckermann,  Schneider,  and  Josting,  who  have  observed  it  this 
year  in  Germany,  the  disease  is  not  of  economic  importance." 

The  British  Board  of  Agriculture  and  Fisheries  made  it  a  notifiable 
disease  in  L907  under  the  Destructive  Insects  and  Pests  Acts.  L877- 
1907.  The  following  report  (Gardeners' Chronicle,  L909)  was  made: 
"The  board  of  agriculture  and  fisheries  de-ire  to  notify  that  2+4 
cases  of  wart  disease  or  black  scab  in  this  year"-  potato  crop  had  been 
reported  to  them  up  to  October  '■'>.  These  cases  have  occurred  in  the 
following  counties:  Shropshire,  60;  Staffordshire,  57:  Lancashire,  50; 
Cheshire,  30;  Warwickshire,  25;  Worcestershire  and  Leicestershire,  I 
each;  Derbyshire,  3;  Merioneth.  2;  and  I  each  in  Perthshire,  Stirling- 
shire, Dumfrieshire,  Cumberland,  Nottingham,  Berkshire,  Flintshire, 
Brecanshire,  and  Glamorgan.  A  few  case-  among  field  crops  h;i\  e  been 
found  in  the  counties  in  which  the  disease  i-  most  common,  but  in  the 
great  majority  of  cases  the  disease  has  occurred  on  allotment-  or  in 
gardens  in  which  potatoes  are  constantly  grown  *  *  *.  The  dis- 
ease has  been  known  in  certain  districts  for  ten  to  fifteen  years,  and 
a-  growers  ha\  e  taken  no  steps  to  che.k  its  progress,  it  is  now  causing 

52] 


b  WART   DISEASE    OF    THE    POTATO. 

serious  loss  *  *  *.  All  cases  of  wart  disease  must  be  notiQed  to 
the  secretary,  board  of  agriculture  and  fisheries  *  *  *.  In  the 
case  of  farmers  who  sell  'seed'  potatoes,  notification  of  the  disease 
is  of  especial  importance,  and  failure  to  notify  must  be  regarded  as  a 
serious  offense  *  *  *.  Persons  concealing  wart  disease  are  liable 
to  prosecution  and  a  penalty  of  £10." 

PRESENT  DISTRIBUTION  OF  THE  DISEASE. 

The  disease  has  been  reported  from  England  (see  p.  5),  from  Scot- 
land in  Perth,  Sterling',  and  Clackmannan  counties;  from  Ireland  in 
Down  County;  from  Wales;  from  German}-  in  Westphalia  and  the 
Rhine  provinces;  and  from  upper  Hungary.  It  has  not  yet  been 
brought  to  the  United  States  so  far  as  known,  but  has  already  crossed 
the  Atlantic  and  become  prevalent  in  Newfoundland,  where  it  was 
lately  discovered  b}7  Dr.  H.  T.  Giissow,  Dominion  botanist,  who  pre- 
sented a  very  interesting  paper  on  the  subject  in  December,  L909, 
before  the  American  Phyto pathological  Society.  Knowing  the  serious 
character  of  the  new  pest  from  personal  observation  of  the  losses 
caused  in  England,  he  promptly  issued  a  warning  bulletin.  The 
Canadian  government  proposes  taking  active  measures  to  prevent  the 
further  introduction  of  the  disease.  Doctor  Giissow  stated  that  there 
have  been  recent  importations  of  seed  potatoes  from  Newfoundland 
into  the  United  States. 

NATURE   OF  THE  PARASITE. 

The  organism  causing  the  disease  is  a  fungus  discovered  in  1890 
in  potatoes  from  upper  Hungary  by  Schilbersky,  who  named  it 
Chrysqphlyctis  enddbiotica  and  placed  it  in  the  lowest  group  of  the 
Chytridiacea?,  Olpidiacese.  By  others  the  fungus  has  been  supposed 
to  be  Oedmnyces  leproides.  We  quote  from  the  excellent  description 
of  Prof.  T.  Johnson,  as  follows:  "The  vegetative  form  consists  of  a 
naked  mass  of  protoplasm  which  may  be  distinguished  in  the  host 
cells  (just  below  the  epidermis)  by  being  denser,  homogeneous,  and 
finely  granular.  It  may  be  seen  abutting  on  the  host  protoplasm, 
and  disputing  with  it,  as  it  devours  it,  occupation  of  the  enlarging 
cell  cavity.  The  protoplasm  follows  and  then  the  cell  wall.  This, 
though  brown,  does  not,  like  the  protoplasm  and  nucleus,  disappear. 
The  starch  grains  art1  the  last  attacked  and  remain  white  and  unin- 
jured for  some  time  in  an  invaded  cell.  The  parasitic  plasmodium 
passes  from  cell  to  cell  by  boring  its  passage  through  the  host  cell 
wall  *  *  *.  It  is  in  this  stage  that  it  stimulates  to  active  cell 
division  the  surrounding  host  cells  and  produces  the  gall  or  wait." 

[Cir,  52] 


; 


Plate  II 


Resting  Spores  of  Wart  Disease. 
Section  through  n  small  tubercle  showing  sporangia.     (After  Giissow.) 


Tuber  Showing  Warty  Excrescences. 
Prom  Joiirnnl  i  il   I  culture,  Jnntmi 


W.\i;i    DISE  \-r   OF    l  ill     POTA  DO.  7 

Daring  the  summer  the  plasmodium  rounds  up,  forming  a  smooth,  yel- 
lowish wall  about  itself.  Later  the  contents  of  these  zoosporangia 
break  up  into  numerous  zoospores,  which  escape  through  ;i  hole  in 
the  wall  and  attack  healthj  potato  tissue. 

"As  tlir  tuber  ripen-,  the  parasite  replaces  the  summer  sporangia 
l>v  resting  ones,  which  carry  the  disease  through  the  winter  and  serve 
to  propagate   it    in    the    spring  *.     The    resting   sporangia, 

.'in  7<>  "  in  diameter,  are  very  numerous  in  diseased  tubers  and  are 
easily  recognizable  with  a  pocket  lens.  Under  the  micro-cope  the 
wall  is  seen  to  be  not  smooth,  but  ridged  or  angular.  These  brown 
ridges  or  hands  form  pari  of  a  kind  of  epispore  which  arises  as  the 
sporangium  ripens,  and  seems  to  be  formed  from  the  residual  con 
tent-  of  the  host  Cell  when  not  also  from  its  cell  wall  as  well  *  *  *. 
The  epispore  is  thus  deposited  from  without  as  a  third  layer  on  the 
thickening  wall  of  the  sporangium.  If  this  more  or  less  artificial 
epispore  is  ignored,  then  one  may  speak  of  the  spore  wall  as 
smooth  *  *  *.  As  a  rule  there  is  only  one  resting  sporangium  in 
a  host  cell;  occasionally  there  are  two."  It  is  exceedingly  difficult  to 
germinate  these  resting  -pore-  artificially.  Professor  Johnson  suc- 
ceeded in  bringing  about  germination  by  placing  them  in  potato  juice. 
lie  write-:  "At  last  the  potato  juice,  exercising  possibly  a  chemo 
tactic  influence,  gave  success;  and  sporangia  with  split  walls  and 
escaping  zoospores  were  found.  These  showed  the  same  sluggish 
movements  observed  in  the  sporangia  of  certain  other  Chytridians 
disturbed  during  their  resting  period.  Each  sporangium  contains 
hundred-  of  more  or  less  pear-shaped  uniciliate  /oospores.  The  zoo- 
spores  measure  from  L.5  to  --'.I  i*  in  diameter.  The  body  is  actively 
amoeboid,  while  the  cilium  is  comparatively  passive."  (T.  Johnson, 
1909.) 

Infect  ion  takes  place  usually  at  the  " eyes "  of  the  tuber  through  t  he 
zoospores  of  either  the  summer  or  resting  sporangia  which  are  found 
infesting  the  surrounding  soil.  It  is  also  believed  by  Johnson  and 
other-  thai  infection  may  take  place  through  the  internal  passage  of 
plasmodia  from  diseased  seed  passing  through  the  stolons  arising  t here- 
from, and  so  into  the  newly  formed  tubers. 

MEANS  OF  EXCLUSION. 

At  the  present  time  the  United  State-  has  no  legislation  that  will 
prevent  the  importation  of  such  a  trouble.  No  quarantine  is  main- 
tained against   plant   diseases,  nor  is  the   Secretary  of   Agriculture 

authorized   to   inspect    or    reject    infected    potatoes,   seeds,   or  nur-er\ 
-lock  of  an\  description. 
[Cir.  .-.--'I 


8 


WART   DISEASE   OF   THE   POTATO. 


The  most  effective  protection  against  the  importation  of  potatoes  is 
the  tariff  of  25  cents  a  bushel.  Yet  in  spite  of  this  the  following 
quantities  have  come  to  our  markets  from  abroad:0 


Country  from  which  imported. 


Bushels. 

Austria-Hungary 34,909 

Belgium 37,275 

Bermuda 68, 964 

Canada 421,106 

Germany 152, 323 

Netherlands 9, 316 

Spain  1,774 

United  Kingdom : 1,192,074 

Other  countries 30, 419 


Year  ended  .Tune  30— 


1900. 


Quantity. 


Total 1, 948, 100 


Value. 


Dollars. 
17,146 

14, 422 

95,  205 

126, 798 

69, 761 

5, 379 

1,558 

504,377 

18,417 


853, 063 


1907. 


Quantity. 


Bushels. 

741 

75 

87,048 

11,393 

39, 419 

5,704 

7.  730 

5,673 

19, 134 


176,917 


Value. 


l>n liars. 

331 

84 

135, 669 

5,970 

19,984 

2,184 

7,408 

3,706 

17, 399 


192, 035 


1908. 


Quantity. 


Bushels. 

1, 723 
6,889 

80,711 
177,102 
62, 059 
38, 892 
11,246 
2,269 
23, 061 


403,952 


Value. 


Dollars. 

740 

3,650 

109,561 

80,000 

38,308 

18, 109 

11,590 

1,321 

19,015 

•283,032 


The  principal  ports  of  entry  of  potatoes  in  1908  were  as  follows: 
Aroostook,  Me.,  67,766  bushels;  Bangor.  Me.,  56,312  bushels;  Boston 
and  Charlestown,  Mass.,  34,901  bushels;  New  York,  202,069  bushels; 
Passamaquoddy,  Me.,  3,286  bushels;  Porto  Rico,  19,285  bushels;  Key 
West,  Fla.,  2,613  bushels;  Arizona,  8,213  bushels;  Champlain,  N.  Y., 
1,390  bushels;  other  ports,  8,057  bushels.     Total.  103,952  bushels.6 

Since  the  interest  and  knowledge  of  the  public  must  be  our  main 
dependence  in  preventing  the  establishment  of  the  potato  wart  in 
America,  it  is  urged  that  all  importers,  dealers,  and  consumers  of 
foreign  potatoes  watch  for  the  disease  and  promptly  report  to  the 
Department  of  Agriculture  at  Washington  any  cases  discovered. 

All  infected  potatoes  should  be  boiled  or  burned.  No  part  of  any 
lot  containing  diseased  potatoes  should  be  used  for  seed  purposes. 

If  the  disease  is  found  on  growing  potatoes,  heroic  measures  should 
be  taken  to  eradicate  the  trouble  by  burning  the  entire  lot  and  planting 
no  more  potatoes  on  that  field  for  six  or  seven  years. 

There  should  be  some  modification  of  our  laws  so  as  to  enable  the 
Secretary  of  Agriculture  to  deal  promptly  with  special  dangers  of  this 
sort  arising  from  the  importation  of  infected  plants. 

"Bulletin  7(5,  Bureau  of  Statistics,  U.  S.  Dept.  of  Agriculture,  p.  54. 
''  Information  furnished  by  Bureau  of  Statistics,  U.  S.  Dept.  of  Agriculture. 
[Cir.  52] 


LITERATURE. 

18!>t>.  Schilbersky.  Kill  neuer  Shorfparasit  der  Kartoffelknollen.  Berichte  tier 
Deutschen  Botanischen Geeellschaft,  vol.  14,  \^'n<,  p.  36. 

\WJ.  (An. .n.  Some  potato  diseases.  The  Journal  of  the  Board  of  Agriculture, 
vol.  9,  1902  ::.  p.  307. 

1902.  Carri  rHEBs,  W.     Diseases  of  trees  and  plants.     The  Journal  of  the  Royal 

Agricultural  Society  of  England,  vol.  63,  1902,  p.  288. 
190:.'.     Potter,    M.   C.      \    new   potato  disease   (Chrysophlyctis  endobiotica).     The 

Journal  of  the  Board  of  Agriculture,  vol.  9,  1902  3,  p.  320. 
L903.     (Anon.)     A  new  potato  disease.     The  Agricultural  Gazette,  vol.  57, 1903,  p.  26. 

1903.  (Anon.      The  warty  disease  of  potatoes.    The  Gardeners'  Chronicle,  vol.  33, 

L903,  p.  329. 
1903.     Carruthers.     Potato  canker  in    Lancashire.     The  Journal   of    the    Royal 

Agricultural  Society  of  England,  vol.  64,  1903,  p.  305. 
1903.     Cooke.     Potato  tumour  (Oedomyces  leproides  Trab.).     The  Journal  of  the 

Royal  Horticultural  Society,  vol.  27,  1903,  p.  sir,. 

1903.  Cooke.     Warty  potato  disease.     The  Gardeners'  Chronicle,   vol.   33,    1903, 

p.  187. 
L903.     MacDougall,  R.  Stewart.     New  fungus  disease  of  potatoes.     Transactions, 
Highland  and  Agricultural  Society  of  Scotland,  ser.  •">,  vol.  15,  1903,  p.  .".12. 

1904.  i  Anon.)     La  plaque  noire  des  pommes  de  terre.     Bulletin  Mensuel  de  1' Office 

de  Renseignements  Agricoles,  vol.  3    1904),  no.  8,  p.  924. 
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Journal,  vol.  15  |  1904),  no.  2,  pp.  605-607. 
1904.     (Anon.)     Black  scab.     The  Agricultural  Gazette,  vol.  59,  L904,  p.  268. 
1904.     (Anon.)     Black  scab  of. potatoes.     The  Agricultural  Gazette,   vol.  59,   1904, 

p.  368 
1904.     (Anon        Black  scab  of  potatoes  (Oedomyces  leproides  Trab.-    Chrysophlyctis 

endobiotica  Schilb. ).     Leaflet  no.  105,  Board  of  Agriculture  and  Fishi 

I Ion,  April.  1904. 

1904.     Eastham,  J    W.     Black  scab  of  potatoes.     Yearl k,  College  of  Agriculture 

and  Horticulture,  Holmes  Chapel,  1904,  pp.  II   13. 
1904.     Massee,  George.    Some  diseases  of  the  potato.     The  Journal  of  the  Royal 

Horticultural  Society,  vol.  29,  1904,  p.  139. 

1904.     Massee.     Black  scab  (Oedoi  roides).     The  Gardeners' Chronicle,  vol. 

35,  1904,  p.  257. 

1904.  R.N.     Warty  potato  diseas       Phe  Gardeners'  Chronicle,  vol.  36, 1904,  p  372. 

1905.  Carbuthers     *  Shrysophlyctis  endobiotica  canker.     The  Journal  of  the  Royal 

Agricultural  Society  of  England,  vol.  66,  1905,  p.  167, 
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1905,  p.  308. 
[Cir.  52]  9 


10  W  ART   DISEASE   OF   THE   POTATO. 

1906.  (Anon.)     Black  scab  of  potatoes  in  North  Wales.     The  Joarnal  of  the  Board 

of  Agriculture,  vol.  13,  1906-7,  p.  441. 

1907.  (Anon.)    Warning.     The  Journal  of  the  Board  of  Agriculture,  vol.  15,  1907-8, 

p.  119. 
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1907,  p.  279. 

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den, Edinburgh,  no.  18,  August,  1907,  pp.  115-119. 

1907.  Dean,  A.  Black  scab  in  potatoes.  The  Gardeners'  Chronicle,  vol.  42,  1907, 
p.  417. 

1907.  Riehm,  E.  Der  Kartorfelkrebs  in  England.  Central) ilatt  fur  P.akteriologie, 
Parasitenkunde,  und  Infektionskrankheiten,  vol .  24, 2d  part,  1907,  pp.  208-213. 

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1907.  Salmon,  E.  S.     "Black  scab"    or    "warty   disease"   of   potatoes.     (Chryso- 

phlyctis  endobiotica     Schilb.).     Bulletin  of  the  County  Councils  of  Kent  and 
Surrey,  1907. « 

1908.  (Anon.)     Black  scab  in  potatoes.     Journal,  Department  of  Agriculture  and 

Technical  Instruction  for  Ireland,  vol.  8,  no.  3,  April,  1908,  pp.  441-443. 

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ture and  Home  Farmer,  vol.  57,  3d  ser.,  1908,  p.  457. 

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Agriculture,  vol.  15,  1908-9,  p.  671. 

1908.  (Anon.)  Potato  scab  and  legislation.  The  Gardeners'  Chronicle,  vol.  43, 
1908,  p.  235. 

1908.  (Anon.)  Some  potato  diseases.  The  Gardeners'  Chronicle,  vol.  44,  1908,  p. 
146. 

1908.  (Anon.)  Warty  disease  in  potatoes.  The  Gardeners'  Chronicle,  vol.  44, 
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1908.  (Anon.)  Black  scab  of  potatoes.  The  Gardeners'  Chronicle,  vol.  44,  1908, 
p.  449. 

1908.  (Anon.)  Varieties  of  scab  in  potatoes.  The  Journal  of  the  Board  of  Agricul- 
ture, vol.  15,  1908-9,  p.  749. 

1908.  (Anon.)  Black  scab  in  potatoes.  Leaflet  No.  91,  Department  of  Agriculture 
and  Technical  Instruction  for  Ireland,  1908." 

1908.  Appel,  O.  Der  Kartorfelkrebs.  Illustrierle  Landwirthschaftliche  Zeitung, 
vol.  28,  1908,  p.  832. 

L908.     Johnson.     Potato  black  scab.     Nature,  1908,  p.  67. 

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1908,  p.  883." 

1908.  Potter,  M.  C.  Note  on  the  warty  disease  and  corky  scab  of  the  potato.  The 
Journal  of  the  New  Castle  Farmers'  Club,  July,  1908. a 

1908.  Potter,  M.  C.  The  warty  disease  of  the  potato.  Gardening,  vol.  130, 
1908,  p.  456. 

1908.  Schneider.  Eine  eigenartige  neue  Kartoffelkrankheit  in  Deutschland. 
Deutsche  Landwirtschaftliche  1'resse,  vol.  35,  1908,  p.  832.a 

liius.     So i:\ukr.     Handbuch  der  Pflanzenkrankheiten,  vol.  2,  p.  116. 


"  Reference  not  verified. 
[Cir.  52] 


w  Ai;  I    DISE  ASE   I  IF    CHE  POTATO.  11 

L908.     Spibckermann.     Ueber  das  \  orkommen  von  <  'hrysophlyctU  thdobiotit  a  Schilb. 

in  Westfalen.     Praktische    Blatter   fur   Pflanzenbau   and    Pflanzenschutz, 

vol.  6,  October,  L908,  p.  I  13 
1909.     Ericksson,  J.     rlvitrota  och    Kriifta  6    potatis.     Centralanstalten   for  Jord- 

bruksfdrsdk,  Flygblad,  no,  8,  February,  1909 
L909.     Grosser.     Der  Kartoffelkrebs:  Zeitschrifl  der  Landwirtschaitliche  Kammer 

furd.  Provinz  Schlesien,  vol.  L3,  L909,  p.  61 1. 
L909.     Gttssow,  II.  T.      \  serious  potato  disease  occurring  in  Newfoundland.     Bul- 
letin 63,  Departmenl  oi    Agriculture,  Central   Experiment   Farm,  Ottawa, 

Canada,  October,  1909 
1909.     Johnson',  T.     Chrysophlyctis  endobiolica  Schilb.  (potato  wart  it  black  scab) 

ami  other  Chytridiaceae.     The  Scientific  Proceedings  of  the  Royal  Dublin 

Societj .  vol.  12,  no.  l  I,  June,  L909 
L909,     BLreitz.     Mitteilung  fiber  einige  Kartoffel  Krankheiten.     Ulustrierte  Land- 

wirthschaftliche  Zietung,  vol.  '-■>,  1909,  p.  I7»i. 
L909.      l'laa  i\  w,  John.      New    fart-  concern  in;,'  warty  di-ea-e  i>l   potato.     The  i.;ir- 

deners'  Chronicle,  3d  Ber.,  vol.  16,  no.  L179,  1909,  p.  7'.». 
L909.     Remy,  T.     Her  I  la.  kit  iuhtl.au,  vol.  1,  Der  Kart.iffell.au.  Berlin,  1909,  \>.  135. 
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trierte  Landwirthschaftliche  Zeitung,  vol.  29,  L909,  p    U5. 
run.     Divers,  W.  II.     Wart  disease  of  potatoes.     The  Gardeners'  Chronicle,  vol. 

47,  1910,  p.  13. 

Approved: 

James  Wilson, 

S(  <■/;  tary  of  Agriculture. 

Washington,  D.  C,  Febntary  'h  1910. 

[fir.  52] 

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